i wasn't planning on purchasing and using them for any new install, i was thinking about using what i already have installed (which would be a great location) and using them to inject power to the DC seasonal stuff

You can use a rectifier to change the voltage from an AC to DC voltage, but the DC volts will still not be completely clean.
The best way is to use a switch mode power supply which will give you clean DC volts and have overload protection as well.